I am trying to get my cargo light to work, I have 12 volts on the orange wire at the switch and at the light socket on one of the contact points where the bulb makes contact in the socket, but the light wont light up, what is the problem? any help would be appreciated

If you have 12 volts at the contact in the bottom center of the bulb socket, then you probably have a bad ground connection from the shell of the bulb socket to a point on the sheet metal. Try running a known-good jumper from the shell of the bulb socket to a good clean ground point. Does that make the bulb light up?

VetteVet, I feel you lurking out there and watching with patient wisdom...so riddle me this...if there was a high resistance present in the power circuit that feeds Jim's cargo light -- say, a frayed wire hanging from strand or two, or a loose connector -- wouldn't it be possible to measure 12 volts at the power contact in the bulb socket with the bulb removed, but then with the bulb in the socket and the switch turned on, the voltage at the power contact in the bulb socket would drop to almost zero due to that pesky high resistance...and there wouldn't be enough voltage at the bulb to light it up?

Thanks for helping me help Jim. I learn a lot by posting my best attempt at answers, but I don't want to lead anyone astray.

I dont understand how this light works, it has two wires going to it and has two contacts on the socket...not just one contact which would be hot and then ground thru the base of the bulb....????? I have 12 volts on one of the contacts which is the orange wire, what is the white wire for? and the second contact on the base of the bulb?any help Vette Vet????

There are some differences in the cargo light and the rest of the interior lights and so the wiring is slightly different. As I understand the operation of the light, the interior (dome) light has to be on in order for the cargo light to get it's ground.

Also it is switched on the ground (white wire side) and the power is wired directly from the dome light (orange wire). I still haven't confirmed that the switch is on the white wire or the orange wire. From what you are saying that you have 12 volts on the orange wire at the switch and at the light socket then it would have to be switched on the orange wire and you should not see 12 volts on the bulb socket with the switch in the off position.

Here's the dilemma, With it wired so the dome light has to be on and the orange wire hot all the way to the cargo light, the light housing would have to be insulated from the metal cab or it would be on all the time. What they did was to wire the ground and power wire directly to the bulb socket and not have the socket touching any ground except the housing.

The best option for me would be to ground the light housing to the cab and switch the orange wire to the light socket. This makes the cargo light independent of the other lights but would have to shut off to avoid draining the battery. Just like the other lights.

Iversaw you are correct about the voltage reading. The volt meter wouldn't read the resistance or voltage drop unless the ground path was connected and current was flowing through it. A good example is the resistance wire to the coil in the points ignitions.
If you read the voltage on the wire with it disconnected and the key on it will read 12 volts but with it connected it will read 8+ volts.

I didn't like the way my interior lights had to be on for my cargo to work so I wired it independent and now the switch behind my head runs my cargo light when I want it...

copied this from chevytalk...

Dome, cargo and courtesy lights are wired differently than most accessories. They have a constant 12 volts applied to the orange wire, and the lights are turned on by grounding the white wire with a switch. This is the opposite of most other items, which are usually grounded all the time, but have the 12 volt power applied by a switch.There is a junction behind the driver's side seat in the cab corner, and it has one orange and one white wire. You can just pop it apart to check for power and ground.- Orange wire always has power*- White is grounded by either the door switch, or by turning the headlight switch counterclockwise.- If white is grounded, the dome and courtesy lights will come on.- If white is grounded, and the switch on the door frame is also on, then the cargo light will also turn on.

thanks Vette, but im confused, all i have to do is ground the white wire ?and yes the orange wire is hot and switched

Your cargo light must not depend on the dome light to be on to work unless the white wire from the dome light is also run to the cargo light housing, which would provide the ground side for the cargo light but you'd still have to switch the orange power wire on to get the cargo light to work.

If you ground a wire from the cargo light to the cab, you won't need the dome light to come on. All you need to do is turn the cargo light switch on.

I didn't like the way my interior lights had to be on for my cargo to work so I wired it independent and now the switch behind my head runs my cargo light when I want it...

copied this from chevytalk...

Dome, cargo and courtesy lights are wired differently than most accessories. They have a constant 12 volts applied to the orange wire, and the lights are turned on by grounding the white wire with a switch. This is the opposite of most other items, which are usually grounded all the time, but have the 12 volt power applied by a switch.There is a junction behind the driver's side seat in the cab corner, and it has one orange and one white wire. You can just pop it apart to check for power and ground.- Orange wire always has power*- White is grounded by either the door switch, or by turning the headlight switch counterclockwise.- If white is grounded, the dome and courtesy lights will come on.- If white is grounded, and the switch on the door frame is also on, then the cargo light will also turn on.